Structural and morphological studies of the dipeptide based L-Pro-L-Val organocatalytic gels and their rheological behaviour

Organocatalytic gels based on the dipeptide sequence L-Pro-L-Val have been studied by two different FTIR techniques. This suggests a different arrangement of the gelator molecules in the self-assembled fibers depending on the organic solvent employed. In acetonitrile and nitromethane the structure of the supramolecular aggregates is similar and provides similar catalytic properties (supramolecularenhancement of basicity). In contrast, the self-assembled fibers obtained in toluene clearly presented a different molecular arrangement consistent with its different catalytic behaviour (enamine-based catalysis). In addition these gels have been studied by microscopy and rheology.

Electro-active nanofibres electrospun from blends of poly-vinyl cinnamate and a cholesteric liquid crystalline silicone polymer

Electrospinning was used to generate polymer nanofibres from blends of poly-vinyl cinnamate (PVCN) and a cholesteric silicone polymer. Only blends that contained at least 40 % of PVCN produced fibres. Both differential scanning calorimetry and electron dispersion spectroscopy data indicate that the samples are miscible over a wide temperature interval. The variation of fibre diameter with concentration is nonlinear with a well-defined minimum corresponding to an 80 % PVCN blend. The fibres are birefringent with Kerr constants similar to that of cholesteric liquid crystals. Although not significant, the Kerr constant increases with increasing silicone polymer concentration.

Microencapsulation of a synbiotic into PLGA/alginate multiparticulate gels

Probiotic bacteria have gained popularity as a defence against disorders of the bowel. However, the acid sensitivity of these cells results in a loss of viability during gastric passage and, consequently, a loss of efficacy. Probiotic treatment can be supplemented using ‘prebiotics’, which are carbohydrates fermented specifically by probiotic cells in the body. This combination of probiotic and prebiotic is termed a ‘synbiotic’. Within this article a multiparticulate dosage form has been developed, consisting of poly(d,l-lactic-co-glycolic acid) (PLGA) microcapsules containing prebiotic Bimuno™ incorporated into an alginate–chitosan matrix containing probiotic Bifidobacterium breve. The aim of this multiparticulate was that, in vivo, the probiotic would be protected against gastric acid and the release of the prebiotic would occur in the distal colon. After microscopic investigation, this synbiotic multiparticulate was shown to control the release of the prebiotic during in vitro gastrointestinal transit, with the release of galacto-oligosaccharides (GOS) initially occurred over 6 h, but with a triphasic release pattern giving further release over 288 h. Encapsulation of B. breve in multiparticulates resulted in a survival of 8.0 ± 0.3 log CFU/mL cells in acid, an improvement over alginate–chitosan microencapsulation of 1.4 log CFU/mL. This was attributed to increased hydrophobicity by the incorporation of PLGA particles.

The bioactivity of composite Fmoc-RGDS-collagen gels

The incorporation of small bioactive peptide motifs within robust hydrogels constitutes a facile procedure to chemically functionalise cell and tissue scaffolds. In this study, a novel approach to utilise Fmoc-linked peptide amphiphiles comprising the bio-functional cell-adhesion RGDS motif within biomimetic collagen gels was developed. The composite scaffolds thus created were shown to maintain the mechanical properties of the collagen gel while presenting additional bio-activity. In particular, these materials enhanced the adhesion and proliferation of viable human corneal stromal fibroblasts by 300% compared to nonfunctionalised gels. Furthermore, the incorporation of Fmoc-RGDS nanostructures within the collagen matrix significantly suppressed gel shrinkage resulting from the contractile action of encapsulated fibroblasts once activated by serum proteins. These mechanical and biological properties demonstrate that the incorporation of peptide amphiphiles provides a suitable and easy method to circumvent specific biomaterial limitations, such as cell-derived shrinkage, for improved performance in tissue engineering and regenerative medicine applications.

Systemic Inflammatory Reaction After Silicone Breast Implant

Systemic inflammation after augmentation mammaplasty with modern silicone implants is not currently recognized. In a prospective controlled study, C-reactive protein and other variables were monitored, aiming to test this hypothesis in a young cohort of patients. Females (18-30 years old, BMI = 18.5-30 kg/m(2), N = 52) were consecutively recruited for breast implant (n = 24, Group I) and for abdominal liposuction (n = 28, Group II/Controls). Patients were interviewed at baseline and followed until 6 months after operation. Variables included demographic and clinical information, surgical outcome, inflammatory markers and autoantibodies. Operations were well tolerated, without surgical or infectious complications. Mean prosthesis size was 258 +/- A 21 ml (range = 220-280) and mean aspirate of liposuction was 1972 +/- A 499 ml (range = 1200-3000). Preoperative, 2-month, and 6-month C-reactive protein concentrations for breast implant patients were 1.3 +/- A 1.2, 4.8 +/- A 3.0, and 4.3 +/- A 6.4 mg/l and for liposuction 3.5 +/- A 2.7, 3.5 +/- A 2.1, and 2.2 +/- A 2.2 mg/l, respectively. Change at 2 months was significant (p = 0.001). Autoantibody investigation failed to reveal remarkable aberrations, except for anticardiolipin elevation, which was nearly symmetrical in the two groups. C-reactive protein levels increased after operation and correlated with proinflammatory and procoagulatory indices. A mild increase in anticardiolipin IgM occurred but differences between populations were lacking. Despite excellent cosmetic outcomes and lack of complications, acute phase reaction could signal ongoing immunogenicity of silicone and long-term monitoring is recommended.

Mechanosensitivity of astrocytes on optimized polyacrylamide gels analyzed by quantitative morphometry

Cells are able to detect and respond to mechanical cues from their environment. Previous studies have investigated this mechanosensitivity on various cell types, including neural cells such as astrocytes. In this study, we have carefully optimized polyacrylamide gels, commonly used as compliant growth substrates, considering their homogeneity in surface topography, mechanical properties, and coating density, and identified several potential pitfalls for the purpose of mechanosensitivity studies. The resulting astrocyte response to growth on substrates with shear storage moduli of G` = 100 Pa and G` = 10 kPa was then evaluated as a function of coating density of poly-D-lysine using quantitative morphometric analysis. Astrocytes cultured on stiff substrates showed significantly increased perimeter, area, diameter, elongation, number of extremities and overall complexity if compared to those cultured on compliant substrates. A statistically significant difference in the overall morphological score was confirmed with an artificial intelligence-based shape analysis. The dependence of the cells` morphology on PDL coating density seemed to be weak compared to the effect of the substrate stiffness and was slightly biphasic, with a maximum at 10-100 mu g ml(-1) PDL concentration. Our finding suggests that the compliance of the surrounding tissue in vivo may influence astrocyte morphology and behavior.

Fluorescent AlPO(4) gels and glasses doped with Rhodamine 6G: Preparation, structural and optical characterization

Fluorescent AlPO(4) xerogels doped with different amounts of Rhodamine 6G (Rh6G) laser dye were prepared by a one-step sal-gel process. In addition, mesoporous AlPO(4) glasses obtained from undoped gels were loaded with different amounts of Rh6G by wet impregnation. Optical excitation and emission spectra of both series of samples show significant dependences on Rh6G concentration, revealing the influence of dye molecular aggregation. At comparable dye concentrations the aggregation effects are found to be significantly stronger in the gels than in the mesoporous glasses. This effect might be attributed to stronger interactions between the dye molecules and the glass matrix, resulting in more efficient dye dispersion in the latter. The interaction of Rh6G with the glassy AlPO(4) network has been probed by (27)Al and (31)P solid-state NMR techniques. New five- and six-coordinated aluminum environments have been observed and characterized by advanced solid-state NMR techniques probing (27)Al-(1)H and (27)Al-(31)P internuclear dipole couplings. The fractional area of these new Al sites is correlated with the combined fractional area of two new Q(3Al)((0)) and Q(2Al)((0)) phosphate species observed in the (31)P MAS NMR spectra. Based on this correlation as well as detailed composition dependent studies, we suggest that the new signals arise from the breakage of Al-O-P linkages associated with the insertion process. (C) 2010 Elsevier B.V. All rights reserved.

Structural matching of 2D electrophoresis gels using deformed graphs

2D electrophoresis is a well-known method for protein separation which is extremely useful in the field of proteomics. Each spot in the image represents a protein accumulation and the goal is to perform a differential analysis between pairs of images to study changes in protein content. It is thus necessary to register two images by finding spot correspondences. Although it may seem a simple task, generally, the manual processing of this kind of images is very cumbersome, especially when strong variations between corresponding sets of spots are expected (e.g. strong non-linear deformations and outliers). In order to solve this problem, this paper proposes a new quadratic assignment formulation together with a correspondence estimation algorithm based on graph matching which takes into account the structural information between the detected spots. Each image is represented by a graph and the task is to find a maximum common subgraph. Successful experimental results using real data are presented, including an extensive comparative performance evaluation with ground-truth data. (C) 2010 Elsevier B.V. All rights reserved.

Graphite-silicone rubber composite electrode: Preparation and possibilities of analytical application

Composite electrodes were prepared using graphite powder and silicone rubber in different compositions. The use of such hydrophopic materials interned to diminish the swallowing observed in other cases when the electrodes are used in aqueous solutions for a long time. The composite was characterized for the response reproducibility, ohmic resistance, thermal behavior and active area. The voltammetric response in relation to analytes with known voltammetric behavior was also evaluated, always in comparison with the glassy carbon. The 70% (graphite, w/w) composite electrode was used in the quantitative determination of hydroquinone (HQ) in a DPV procedure in which a detection limit of 5.1 x 10(-8) mol L-1 was observed. HQ was determined in a photographic developer sample with errors lower then 1% in relation to the label value. (c) 2007 Elsevier B.V. All rights reserved.

THE POTENTIALITIES OF USING A GRAPHITE-SILICONE RUBBER COMPOSITE ELECTRODE IN THE DETERMINATION OF PROPRANOLOL

A graphite silicone-rubber composite electrode (GSR) was used for the determination of propranolol in drug formulation. Cyclic voltammetry (CV) at the GSR presented an irreversible oxidation peak at + 0.8V vs. SCE, in Britton Robinson (B-R) buffer pH 7.4. The quantitative determination was carried out using differential pulse voltammetry (DPV). Under optimized parameters a linear dynamic range from 5.0 to 80.6 mu mol L(-1) with a detection limit of 1.1 mu mol L(-1) was observed. A repeatability of 4.5 +/- 0.1 mu A (n = 10) peak current was found after 10 successive DPV voltammograms of propranolol in the same solution after surface renovations. Using the proposed electrode, propranolol was quantified in a pharmaceutical formulation with results that agreed within 95% confidence level (t-test) with those from an official method.

Analytical Potentialities of Carbon Nanotube/Silicone Rubber Composite Electrodes: Determination of Propranolol

A new composite electrode based on multiwall carbon nanotubes (MWCNT) and silicone-rubber (SR) was developed and applied to the determination of propranolol in pharmaceutical formulations. The effect of using MWCNT/graphite mixtures in different proportions was also investigated. Cyclic voltammetry and electrochemical impedance spectroscopy were used for electrochemical characterization of different electrode compositions. Propranolol was determined using MWCNT/SR 70% (m/m) electrodes with linear dynamic ranges up to 7.0 mu molL(-1) by differential pulse and up to 5.4 mu molL(-1) by square wave voltammetry, with LODs of 0.12 and 0.078 mu molL(-1), respectively. Analysis of commercial samples agreed with that obtained by the official spectrophotometric method. The electrode is mechanically robust and presented reproducible results and a long useful life.

Implante de tubo de silicone com e sem colágeno na regeneração de nervos em eqüinos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento de sistemas líquido-cristalinos empregando silicone fluido de co-polímero glicol e poliéter funcional siloxano

DEVELOPMENT of LIQUID-CRYSTALLINE SYSTEMS USING SILICON GLYCOL COPOLYMER and POLYETHER FUNCTIONAL SILOXANE. For the construction of the phase diagrams, the method of the aqueous titration was used. There were prepared 5 ternary diagrams, varying the surfactant and the oil phase. The liquid-crystalline phases were identified by polarized light microscopy. The formulations prepared with silicon glycol copolymer, polyether functional siloxane (PFS) and water (S(1)) and with diisopropyl adipate, PFS and water (S(4)) presented liquid-crystalline phases with lamellar arrangement. Moreover, after 15 days in hot oven (37 degrees C), the formulations presented hexagonal arrangement, evidencing the influence of the temperature in the organization of the system.

The influence of external ultrasound on the histologic architecture of the organic capsule around smooth silicone implants: Experimental study in rats

Background Capsular contracture is the main complication related to breast silicone implants, and its prevention remains a medical challenge. The authors present experimental research examining the effect of external ultrasound on the formation and contracture of peri-implant capsules.Methods In this study, 42 male Wistar rats had a 2-mm smooth surface implant placed in a dorsal submuscular pocket. They then were separated into ultrasound'' and control'' groups that received repeated external applications either with or without the ultrasound power on. Ultrasound applications were given three times a week for a period of 90 days. After that, both groups were housed under the same conditions with no application scheduled. Five animals of each group, killed at 30, 60, 90, and 180 days, had their implants removed along with the capsule, which received a special histologic preparation via annular sectioning that provided wide circumferential observation of the capsular tissue. Sections were stained with hematoxylin/eosin stain, Masson's trichrome stain, and Pricrosirius Red stain for regular microscopic evaluation under normal and polarized light.Results Histologic data showed that capsules from the ultrasound and control groups had statistically significant differences. Ultrasound application developed a capsular architecture similar to that shown within textured silicone implants, and its effect had an early definition with subsequent stabilization.Conclusion The authors conclude that early and repeated external ultrasound application enhances the thickness, cellular count, and vascularity of smooth silicone capsular tissue, whereas it diminishes the pattern of parallel orientation of collagen fibers.